1. Field of the Invention
The present invention relates to reinforced resin compositions containing as a main component a polyethylene terephthalate-type resin; the compositions have excellent heat resistance and uniform appearance.
2. Description of the Prior Art
Glass fiber-reinforced polyethylene terephthalate resins have been used widely for their excellent mechanical properties and chemical resistance. However, products obtained by molding these glass fiber-reinforced resins at mold temperatures lower than 100.degree. C. have a heat distortion temperature of about 100.degree. C. and are poor in the heat resistance. Furthermore, when molded articles of uneven thickness are prepared from these reinforced resins, the thin portion tends to be semi-transparent and the thick portion white only in the interior. The thus obtained molded articles are nonuniform in appearance and are not preferred from the aesthetic viewpoint. On the other hand, molded articles obtained by elevating the mold temperature to a level higher than about 120.degree. C. have a heat distortion temperature of about 230.degree. C., and even molded articles having a thin portion have a white uniform appearance with excellent luster. Therefore, when high heat resistance and uniform appearance are required, the molding operation is ordinarily carried out at a high mold temperature of 130.degree. C. to 150.degree. C., however a high-temperature mold is costly to operate and as such represents a serious disadvantage.
Recently, additives capable of improving the heat resistance of polyethylene terephthalate resins, such as metal salts of organic carboxylic acids and inorganic compounds, have been used. When incorporated these additives allow for some improvement in heat resistance, molding temperature dependency and appearance of the articles. More specifically, even if a polyethylene terephthalate resin composition containing such additives is molded at a low mold temperature, the degree of whitening in the thick portion of the molded article is increased and the heat resistance is also improved to some extent. However, when a thin molded article containing an additive such as a metal salt of an organic carboxylic acid or an inorganic compound is prepared according to this method, if the mold temperature is low, the heat resistance of the molded article obtained is still poor, the article is semi-transparent or the interior thereof is slightly whitened. The appearance is not uniform. Especially in case of a molded article which is of uneven thickness, since the appearance of the thin portion is different from that of the thick portion, the thus molded article is visually nonuniform in appearance and as such is rather aesthetically inferior.